1. Field of the Invention
This invention relates to a matrix plasma display panel using a gas discharge for producing light emission.
The present application claims priority from Japanese Application No. 2002-29698, the disclosure of which is incorporated herein by reference for all purposes.
2. Description of the Related Art
Currently, AC matrix plasma display panels using a gas discharge for producing light emission (hereinafter referred to as xe2x80x9cPDPxe2x80x9d) has appeared on the market as an oversized and slim display for color screen.
FIGS. 16 and 17 show the cell construction of the AC matrix PDP which has already been proposed by the same applicant as the present application, FIG. 16 being a front view of the cell construction, and FIG. 17 being a sectional view taken along the Vxe2x80x94V line of FIG. 16.
In FIGS. 16 and 17, a front glass substrate 1 serving as the display surface of the PDP is provided on its back surface with a plurality of row electrode pairs (X, Y) which are arranged in parallel, each extending in a row direction of the front glass substrate 1 (the right-left direction in FIG. 16).
Each of the row electrodes X includes transparent electrodes Xa each of which is formed of a transparent conductive film made of ITO or the like constructed in a letter-T shape, and a bus electrode Xb which is formed of a metal film extending in the row direction of the front glass substrate 1 and connected to a narrowed base end of each of the transparent electrodes Xa.
Likewise, each of the row electrodes Y includes transparent electrodes Ya each of which is formed of a transparent conductive film made of ITO or the like constructed in a letter-T shape, and a bus electrode Yb which is formed of a metal film extending in the row direction of the front glass substrate 1 and connected to a narrowed base end of each of the transparent electrodes Ya.
The row electrodes X and Y are arranged in alternate positions in the column direction of the front glass substrate 1 (the vertical direction in FIG. 16). In each row electrode pair (X, Y), the transparent electrodes Xa and Ya are regularly arranged along the corresponding bus electrodes Xb and Yb. The transparent electrodes Xa and Ya paired extend toward each other such that leading ends of widened portions of the respective electrodes Xa and Ya are opposite to each other with an interposed discharge gap g having a required width.
On the back surfaces of the front glass substrate 1, a dielectric layer 2 is also formed to cover the row electrode pairs (X, Y). On the back surface of the dielectric layer 2, an additional dielectric layer 2A is formed to protrude from the back surface of the layer 2 and extends in parallel to the bus electrodes Xb, Yb, in a position opposite to back-to-back bus electrodes Xb and Yb of the adjacent row electrode pairs (X, Y) plus opposite to an area between the back-to-back bus electrodes Xb and Yb concerned.
A protective layer 3 made of MgO is also provided on the back surfaces of the dielectric layer 2 and the additional dielectric layer 2A.
The front glass substrate 1 is situated in parallel to a back glass substrate 4 having a surface facing the display surface on which a plurality of column electrodes D are arranged in parallel at predetermined intervals and each extend in a direction at right angles to the row electrode pairs (X, Y) (or the column direction) in a position opposite the paired transparent electrodes Xa and Ya of the row electrode pairs (X, Y).
On the surface of the back glass substrate 4 on the display surface side, a white column-electrode protective layer 5 covers the column electrodes D, and partition walls 6 are formed on the protective layer 5.
The partition wall 6 is constructed in a ladder-shaped pattern by vertical walls 6a each extending in the column direction in a position between adjacent column electrodes D arranged in parallel to each other; and transverse walls 6b each extending in the row direction in a position opposite the additional dielectric layer 2A.
The ladder-patterned partition walls 6 partition a space defined between the front and back glass substrates 1 and 4 into sections each corresponding to the paired transparent electrodes Xa and Ya of each row electrode pair (X, Y), to define quadrangular discharge cells C.
A phosphor layer 7 is provided to cover five faces facing each discharge cell C: a face of the column-electrode dielectric layer 5 and the four inner side faces of the vertical walls 6a and transverse walls 6b of the partition wall 6. The phosphor layers 7 are arranged in order of a red color, a green color and a blue color along the row direction for each discharge cell C.
The discharge space S is filled with a discharge gas including xenon Xe.
In the PDP, an addressing discharge is generated between the row electrode Y and the column electrode D. Then, a sustaining discharge is generated between the row electrodes X and Y in each discharge cell of the discharge cells C having wall charges existing on the dielectric layer 2 as a result of the addressing discharge (lighted cell), to cause the red, green and blue phosphor layers 7 to emit light to thereby form an image in a matrix display.
In the PDP constructed as described above, the dielectric layer 2 provided for AC driving is formed by means of processes of printing a low-melting glass paste on the back surface of the front glass substrate 1 and then burning it, to have a thickness sufficiently larger than that of the row electrode X, Y, for example, a thickness around twenty to thirty times larger than that of the row electrode X, Y.
The PDP has the construction in which each of the phosphor layers 7 is formed on the back glass substrate 4 in order to reduce degradation of the phosphor layer 7 due to the ion bombardment in a sustaining discharge for an long life of the PDP, and also the dielectric layer 2 has a flat surface facing each discharge cell C in order to improve luminous efficiency of the phosphor layer 7, and a surface discharge d is produced between the row electrodes X and Y as illustrated in FIG. 17.
However, in the PDP constructed as described above, because the phosphor layers 7 are provided on the back glass substrate 4 in order to increase a life of the PDP and also the sustaining discharge between the row electrodes X and Y is created in a surface discharge mode, the sustaining discharge in the surface discharge mode requires a driving voltage higher than that required when a sustaining discharge between the row electrodes X and Y is created in an opposite discharge mode, leading to a problem of a need of expensive circuit components capable of withstanding high voltage.
The present invention has been made to solve the above-described problems associated with the surface-discharge matrix plasma display panels.
Accordingly, it is an object of the present invention to provide a surface-discharge-type matrix plasma display panel capable of producing a discharge between row electrodes at low driving voltage.
To attain this object, the present invention provides a plasma display panel including: a pair of substrates opposite to each other with a discharge space interposed therebetween; a plurality of row electrode pairs provided on an inner surface of one substrate of the pair of the substrates, regularly arranged in a column direction and each extending in a row direction to form a display line; a plurality of column electrodes provided on an inner surface of the other substrate of the pair of the substrates, regularly arranged in the row direction and each extending in the column direction to intersect the row electrode pairs and form unit light-emitting areas in the discharge space at the respective intersections; and a discharge gap provided between a pair of the row electrodes constituting each of the row electrode pairs in each unit light-emitting area. The plasma display panel according to a first feature of the present invention comprises: a dielectric layer provided on the inner surface of the one substrate to cover the row electrode pairs, and having a thickness in a portion opposite each of the discharge gaps smaller than a thickness in portions positioned on both sides of the portion opposite the discharge.
In the plasma display panel of the first feature, a discharge pulse is applied between the row electrodes constituting each row electrode pair provided on the one substrate to initiate a surface discharge on a surface of the dielectric layer facing the discharge space. The resulting discharge causes a phosphor layer formed on the other substrate to emit light for generation of an image on the display surface of the panel.
On the face of the dielectric layer facing the discharge space, the dielectric layer is designed such that the portion opposite to each discharge gap between the paired row electrodes has a thickness smaller than that of the other portions on both sides of it so as to make a recess. Due to this design, in a discharge created between the row electrodes of the row electrode pair, the discharge occurring inside the recess is produced in a mode close to an opposite discharge mode.
According to the first feature, in the plasma display panel adopting the surface discharge mode with the aim of extending its life, a discharge occurring in a position opposite to the discharge gap between the row electrodes is closely analogous to an opposite discharge mode, which is thus increased in electric field strength. For this reason, the present invention requires a lower driving voltage for a discharge than that in prior art surface-discharge-type plasma display panels, and eliminates the need for expensive circuit components withstanding high voltage.
Further, with a decrease in a driving voltage for causing a discharge between the row electrodes, a reset-discharge voltage decreases, leading to improvement in dark contrast on a display screen of the panel.
To attain the aforementioned object, the plasma display panel according to a second feature comprises, in addition to the configuration of the first feature, a recess provided in a position opposite each of the discharge gaps on the surface of the dielectric layer facing the discharge space to make a thickness of the portion of the dielectric layer opposite the discharge gap smaller than a thickness of the portions of the dielectric layer positioned on both sides of the portion opposite the discharge gap.
According to the second feature, a recess facing the discharge space is formed in the portion of the dielectric layer opposite the discharge gap between the row electrodes. Hence, when a discharge is created between the row electrodes, the discharge occurring inside the recess is produced in a mode close to an opposite discharge mode. This design allows the surface-discharge-type plasma display panel to increase an electric field strength of a discharge between the row electrodes to thereby provide a decreased driving voltage for the discharge.
To attain the aforementioned object, the plasma display panel according to a third feature has, in addition to the configuration of the second feature, a configuration that the recess is formed in a band-like shape extending parallel to the row direction through the adjacent unit light-emitting areas in the row direction.
According to the third feature, a discharge between the row electrodes occurring in the recess formed in the dielectric layer in a band-like shape extending parallel to the row direction, is produced in a mode close to an opposite discharge mode. Thus, the surface-discharge-type plasma display panel is allowed to increase an electric field strength of a discharge between the row electrodes for a decrease in a driving voltage for the discharge.
Further, the band-shaped recess is formed so as to extend through the adjacent unit light-emitting areas in the row direction. With this design, for example, even when the unit light-emitting areas adjacent to each other in the row direction are blocked from each other by an additional dielectric layer which is formed on the dielectric layer or a partition wall defining the unit light-emitting areas, the recess provides communication between the adjacent unit light-emitting areas. Thus it is possible to make full use of the so-called priming effect of triggering a discharge to occur in a unit light-emitting area and transfer to the adjacent unit light-emitting area.
To attain the aforementioned object, the plasma display panel according to a fourth feature has, in addition to the configuration of the second feature, a configuration that the recess is formed separately in each unit light-emitting area.
According to the fourth feature, a discharge between the row electrodes occurring in the recess formed in the dielectric layer separately in each unit light-emitting area, is produced in a mode close to an opposite discharge mode. Thus, the surface-discharge-type plasma display panel is allowed to increase an electric field strength of a discharge between the row electrodes for a decrease in a driving voltage for the discharge.
To attain the aforementioned object, the plasma display panel according to a fifth feature comprises, in addition to the configuration of the second feature, a pair of protrusions projecting into the discharge space in positions on the surface of the dielectric layer facing the discharge space corresponding to leading ends of the respective row electrodes facing each other with the interposed discharge gap, the recess being formed between the pair of protrusions.
According to the fifth feature, due to a pair of protrusions respectively formed in the positions opposite the leading ends of the row electrodes on the dielectric layer, the dielectric layer has a thickness in its portions opposite the leading ends concerned larger than that in its other portions, so that the recess sandwiched between the pair of protrusions is formed in a portion of the dielectric layer opposite the discharge gap.
A discharge between the row electrodes occurring in the recess sandwiched between the pair of protrusions of the dielectric layer is produced in a mode close to an opposite discharge mode. Thus, the surface-discharge-type plasma display panel achieves an increase in electric field strength of a discharge between the row electrodes to decrease a driving voltage for the discharge.
To attain the aforementioned object, the plasma display panel according to a sixth feature has, in addition to the configuration of the fifth feature, a configuration that the dielectric layer has a thickness in a portion opposite a base end of each of the row electrodes smaller than that in the portion opposite the leading end of the row electrode and with the protrusion formed on.
According to the sixth invention, a discharge between the row electrodes occurring in the recess sandwiched between the pair of protrusions of the dielectric layer is produced in a mode close to an opposite discharge mode. Thus, the surface-discharge-type plasma display panel achieves an increase in field strength of a discharge between the row electrodes to decrease a driving voltage for the discharge.
Further the dielectric layer has a smaller thickness in the portions opposite the base ends of the row electrodes, namely, in the portions on both sides of the pair of protrusions, in each unit light-emitting area. This design allows for an increase in the path length of the discharge between the row electrodes, extending between the portions of the dielectric layer situated on both sides of the pair of protrusions. Such a long discharge path provides improvement in luminous efficiency of the phosphor layer formed on the other substrate with the column electrode formed on.
To attain the aforementioned object, the plasma display panel according to a seventh feature has, in addition to the configuration of the sixth feature, a configuration that the dielectric layer has a thickness in the portion opposite the discharge gap and with the recess formed thereon smaller than a thickness in the portion opposite the base end of the row electrode.
In the seventh feature, the dielectric layer is designed to decrease in thickness of the portion positioned opposite the discharge gap and between the pair of protrusions, that is, the recess formed between the pair of protrusions is increased in depth. Accordingly, a discharge between the row electrodes occurring in the increased-depth recess is produced in much closer to the opposite discharge mode. Thus, the surface-discharge-type plasma display panel achieves an increase in field strength of a discharge between the row electrodes to decrease a driving voltage for the discharge.
To attain the aforementioned object, the plasma display panel according to an eighth feature comprises, in addition to the configuration of the first feature, a recess provided in a portion opposite to a base end of each row electrode on the surface of the dielectric layer facing the discharge space in each unit-light-emitting area to make a thickness of the portion of the dielectric layer opposite the base end of the row electrode smaller than a thickness of a portion of the dielectric layer opposite a leading end of the row electrode.
According to the eighth feature, the recesses are respectively formed in the portions of the dielectric layer opposite the base ends of the row electrodes. The recesses provide a decrease of the thickness of the portions of the dielectric layer on both sides of the portions respectively opposite the leading end of each row electrode. This design allows for an increase in the path length of the discharge between the row electrodes, extending between the portions of the dielectric layer situated on both sides of the portions respectively opposite the leading ends of the row electrodes. Such a long discharge path provides improvement in luminous efficiency of the phosphor layer formed on the other substrate with the column electrode formed.
To attain the aforementioned object, the plasma display panel according to a ninth feature has, in addition to the configuration of the eighth feature, a configuration that the recess provided in the portion of the dielectric layer opposite each of the base ends of the row electrode is shaped in a band-like form extending in parallel to the row direction through the adjacent unit light-emitting areas in the row direction.
According to the ninth feature, due to the design that the band-shaped recess formed in the dielectric layer extends through the adjacent unit light-emitting areas in the row direction, even when the adjacent unit light-emitting areas in the row direction are blocked from each other by the partition wall provided for defining the unit light-emitting areas or an additional element formed on the dielectric layer, for example, the recess provides communication between the adjacent unit light-emitting areas. Thus it is possible to make full use of the so-called priming effect of triggering a discharge to occur in a unit light-emitting area and transfer to the adjacent unit light-emitting area.
To attain the aforementioned object, the plasma display panel according to a tenth feature has, in addition to the configuration of the first feature, a configuration that the portion of the dielectric layer with the smaller thickness opposite the discharge gap has a center point offset from a center point of the discharge gap.
According to the tenth feature, the center point of the recess formed in the thinner portion of the dielectric layer opposite the discharge gap is offset from the center point of the discharge gap, but the discharge between the row electrodes occurs in a mode close to the opposite discharge mode in the recess of the dielectric layer, resulting in a decreased driving voltage for the discharge.
These and other objects and features of the present invention will become more apparent from the following detailed description with reference to the accompanying drawings.